Dry-powder inhalers are well known in the prior art. Various types exist. A first type of inhaler contains a reservoir receiving many doses of powder, the inhaler being provided with metering means making it possible, on each actuation, to remove one dose of said powder from the reservoir, so as to bring said dose into an expulsion duct in order to be dispensed to the user. Another type of inhaler consists in packaging the doses of powder in individual pre-dosed reservoirs, then in opening one of the reservoirs each time the inhaler is actuated. That implementation seals the powder more effectively since each dose is opened only when it is about to be expelled. In order to make such individual reservoirs, various techniques have already been proposed, such as an elongate blister strip or blisters disposed on a rotary circular disk.
Inhalers including individual reservoirs, such as capsules, that are loaded into the inhaler just before said reservoir is used are also described in the prior art. The advantage of such devices is that it is not necessary to store all of the doses inside the appliance, such that said appliance can be compact. Obviously however, the inhaler is more difficult to use, since the user is obliged to load a capsule into the inhaler before each use.
All existing types of inhalers, including those described above, present both advantages and drawbacks associated with their structures and with their types of operation. Thus, with certain inhalers, there is the problem of accuracy and of reproducibility for the dose on each actuation. In addition, the effectiveness of the dispensing, i.e. the fraction of the dose that effectively penetrates into the user's lungs in order to have a beneficial therapeutic effect, is also a problem that exists with a certain number of inhalers.
A solution for solving that specific problem has been to synchronize the expulsion of the dose with the inhalation of the patient. Once again, that can create drawbacks, in particular in that type of device, the dose is generally loaded into an expulsion duct before inhalation, then expulsion is synchronized with inhalation. That means that if the user drops, shakes, or manipulates the inhaler in an undesirable or inappropriate manner between the moment when the user loads the dose (either from a multi-dose reservoir or from an individual reservoir) and the moment when the user inhales, then the user risks losing all or part of the dose, with said dose possibly being spread about inside the appliance. In that event, there can exist a high risk of overdosing the next time the device is used. The user who realizes that the dose is not complete will load a new dose into the appliance, and while the new dose is being inhaled, a fraction of the previous dose that was lost in the appliance could thus be expelled at the same time as the new dose, thereby causing an overdose. In the treatments envisaged, such overdosing can be very harmful, and the authorities in all countries are issuing ever-stricter requirements to limit the risk of overdosing as much as possible. With regard to opening the individual reservoirs, it has been proposed to peel off or to unstick the closure layer. That presents the drawback of difficulty in controlling the forces to be applied in order to guarantee complete opening, without running the risk of opening the next reservoir, particularly if the opening means need to be actuated by inhalation. In a variant, it has been proposed to perforate the closure layer or wall. That can present the drawback that the cut wall-portions risk retaining a fraction of the dose inside the reservoir, so that metering accuracy and reproducibility are therefore not guaranteed.
Documents FR-2 881 120, WO 2008/012458, U.S. Pat. No. 6,012,454, and FR-2 896 419 describe prior-art devices.